Concentric manipulation and monitoring of protein-loaded superparamagnetic cargo using magnetophoretic spider web

A lab-on-a-chip (LOC) magnetophoretic system for the remotely controllable transport of magnetic particles actuated by thin permalloy magnetic tracks has been developed as a novel architecture composed of radii and spiral tracks resembling a spider web network, where the network tracks have the asymmetric and anisotropic magnetic properties for the directional transportation of particles (cargos). A planar Hall resistance (PHR) sensor is integrated with the web networks, and the manipulation and detection are achieved via superparamagnetic particles with dual functions as a biomolecule cargo for transportation and labels for monitoring. The streptavidin protein-coated magnetic particles are precisely manipulated toward the PHR sensor surface via the radii and spiral tracks by applying an external rotating magnetic field. The stray field was analyzed in terms of the particle coverage on the sensor surface, where the sensor signal linearly varies with the number of particles on the sensor surface. This allows the effective collection of low-density biomolecule carriers to one specific point and monitors the accumulated carriers. The developed novel technology could affect multiple fields, including bioassays, cell manipulation and separation and biomechanics. Arranging linear and spiral-shaped magnetic tracks in a web-like network enables simultaneous monitoring and manipulation of biomolecules. As lab-on-a-chip devices get increasingly smaller, it is becoming more difficult to move tiny liquid droplets in them. CheolGi Kim of the Daegu Gyeongbuk Institute of Science and Technology in South Korea and co-workers has developed a way to precisely transport proteins and label them for biosensing. They used streptavidin proteins coated superparamagnetic carriers and then manipulated them on a magnetic surface that resembled a microscale spider web, consisting of concentric tracks centred on a central magnetoresistive sensor. Applying an external rotating magnetic field enabled on-demand movement of the particles towards the sensor, where they were quantified. This could enhance the sensitivity of biosensing schemes by collecting biomolecules, even when they are present in low densities. Novel magnetophoretic device resembling a spider web network, being integrated with planar Hall resistance sensor, has been developed for the simultaneous concentric transportation and monitoring of superparamagnetic streptavidin-loaded cargos (particles). The multilayer sensor and permalloy network tracks have been fabricated by successive micropatterning processes of film deposition and photolithography. The transporting particles are precisely manipulated on the magnetic tracks towards the sensor by an external magnetic field, where the sensor signal varies with the accumulated particle number. This effective collection and monitoring platform could open novel bioassays overcoming limitation of Brownian transportation of biomolecules to the sensor surface.